Polyvinyl acetal resin sheets containing tributyl citrate



Patented Oct. 28, 1941 POLYVINYL ACETAL RESIN SHEETS CON- TAINING TRIBUTYL CITRATE Henry B.

Eastman Kodak Smit Rochester, N. Y., assignor to Company, Rochester, N. corporation of New Jersey No Drawing. Application February 1, 1938, Serial No. 188,190

2 Claims.

This invention relates to plastic compositions, and more particularly to compositions comprising a polyvinyl acetal resin and a conditioning agent,

One object of this invention is to produce compositions of matter which may be made into permanently transparent, strong and flexible sheets or films of desired thinness which are substantially waterproof, are unafiected by ordinary photographic fiuids and possess the desired properties of a support for sensitive photographic coatings. Another object of my invention is to produce compositions of matter which can be made into sheets suitable for use in laminated, shatter-proof glass. Still another object is to produce compositions which can be rolled, extruded, molded or otherwise worked into relatively thick sheets and massive plastics. A further object is to produce compositions suitable for use in lacquers, artificial silk fllaments,.wrapping tissues and the like. Other objects will hereinafter appear.

I have discovered that tributyl citrate is a useful conditioning agent for polyvinyl acetal resins. Not only does it serve as a plasticizer in the accepted sense of the term, increasing the flexibility and toughness of polyvinyl acetal resin films, sheets, or other objects or masses containing it, but when used in amounts of about 40 parts or more per 100 parts of certain of the polyvinyl acetal resins, namely the polyvinyl acetal resins in which a predominating proportion of the acetal groups are butyraldehyde acetal groups, it has an unusual and remarkable effect which I may call elasticizing. That is to say, a sheet of a polyvinyl butyraldehyde acetal resin containing about 40 or more parts acetone-methanol mixtures, ethylene chloridemethanol mixtures, etc., about 300 to 500 or more parts of the solvent or solvent used per 100 parts of the resin.

to 100 parts or moreof From about 3 of tri-. butyl citrate per 100 parts of resin possesses themixture bein tributyl citrate per 100 55 6 and '7.

parts of resin may be employed, depending upon the nature of the resin and the purpose for which the sheets are to be used. Suitable proportions of tributyl citrate for any resin and any purpose may be readily determined by experiment. For

the manufacture of sheets suitable for photographic film base, from 3 to 25 parts of tributyl citrate per 100 parts of resin are suitable. The resin solution is cast as a sheet, the solventevaporated, and the sheet stripped from the casting surface.

Sheets for use in laminated glass may be formed by casting, or may be made without the use of volatile solvent by extrusion, for example in the manner set forth in application Serial No. 147,934 of John S. Kimble and Ernest C. Blackard, filed June 12, 1937. For instance, 40 or more parts of tributyl citrate and 100 parts of a polyvinyl butyraldehyde acetal resin may be mixed in a suitable, jacketed mixer at a low temperature, for example 10 C., and the, mixture may then be worked on hot rolls, in the manner described in U. S. Patent 2,048,686 of F. R. Conklin, until complete homogenization has taken place. The mass thus produced may then be extruded through an annular die, and the tube so formed slit to form a sheet.

The polyvinyl acetal resins can be prepared by reacting polyvinyl alcohol with an aldehyde in 80 the presence of an acetal condensation catalyst,

e. g., a mineral acid. These resins can also be prepared by simultaneously de-esterifying a polyvinyl aliphatic ester and reacting the deesterification product with an aldehyde in the presence of a de-esterifying catalyst and acetal condensation catalyst. Mineral acids are catalysts for both de-esterification and acetal formation. Among the polyvinyl acetal resins with which tributyl citrate is useful may be men- 'tioned, as illustrative examples,' the. polyvinyl formaldehyde acetal resins, the polyvinyl ace-,-

taldehyde acetal resins, the polyvinyl formalde hyde acetaldehyde mixed acetal resins, the polyvinyl butyraldehyde acetal resins, the polyvinyl 5 butyraldehyde acetaldehyde mixed acetal resins, and the polyvinyl cyclohexanone butyraldehyde mixed acetal resins.

Examples. of the preparation of polyvinyl formaldehyde acetal resins may be found in U. S. Patent 1,955,068, Examples 1, 4 and 5; in U. S. Patent.2,036,092, Examples 1, 2, 3, 'l and 8; in British. Patent 454,691, Examples 1, 2, 3, 4, 5, 6 and 7; in British Patent 404,279, Example 3; and in British Patent 436,072,'Examples 1, 2, 3, 4, 5,

Examples of the preparation of polyvinyl acetaldehyde acetal resins may be found in U. 8. Patent 2,044,730, Example 1; U. S. Patent 1,955,- 068, Example 2; U. S. Patent 2,036,092, Examples 4, 5 and 6; British Patent 466,598, Examples 1, 2, 3, 4 and 7; British Patent 404,279, Examples 1,

2, 4, 5, 6, '7 and 8; U. S. Patent 1,990,399; and

French Patent 808,578, Examples 1, 2 and 3.

An additional example of the preparation of a polyvinyl acetaldehyde acetal resin is as follows:

100 lbs. of polyvinyl acetate, the viscosity of whose molar solution in benzene was 45 centipoises, was dissolved in 300.1bs. of 95% ethyl alcohol. To this solution were added 30lbs. of paraldehyde and 25 lbs. of 35% HCl. The reaction mixture was allowed to stand for 4 days at 40 C., after which it was diluted with ethyl alcohol, and the resin precipitated by pouring into cold water, washed and dried. Analysis showed the resin to have an acetate group content equivalent to 2.1% by weight of polyvinyl acetate and a hydroxyLgroup content equivalent 'to 12.9% by weight of polyvinyl alcohol.

Examples of the preparation of polyvinyl formaldehyde acetaldehyde mixed acetal resins may be found in British Patent 430,136, Examples 1, 2, 3, 4, 5 and 6; British Patent 445,565, Example 2; British Patent 465,873, Examples 1, 2, 3, i 5 and 6; French Patent 808,586, Examples 1, 2, 4, 5, 6, 12, 13, 14, 15, 16, 17, 18, and 19.

Additional examples of the preparation of polyvinyl formaldehyd acetaldehyde mixed 7 acetal resins are given in the application of Ralph H. Talbot, Serial No. 85,960, filed June 18, 1936, as follows:

Example 1 "100 parts (1.16 mol. calculated as monomeric vinyl acetate) 'of a polyvinyl acetate (45 centipoises), 100 parts of ethyl alcohol, 180 parts of ethyl acetate, 34 parts (.77 mol. as monomeric acetaldehyde) of paracetaldehyde and 5.8 parts (.196 mol. as monomeric formaldehyde) of paraformaldehyde were placed in an enamelled vessel and brought into solution by stirring. When solution was complete, 10 parts of sulfuric acid (sp. g. 1.84) in 10 parts of water were added, and the mixture stirred. The mixture was maintained at a temperature of 40 C. for 144 hours. The contents of the vessel were then diluted with about two and a half volumes of acetone, andthe mixture precipitated into water. The precipitated resin was washed free from impurities by repeated changes of cold water, and dried. The resin, when analyzed, gave a hydroxyl group content equivalent to about 6.4 per cent by weight of polyvinyl alcohol, an acetate group content equivalent to about 4.0 per cent by weight of polyvinyl acetate, a formaldehyde acetal group content equivalent to about 15.9 per cent by weight of polyvinyl formaldehyde acetal and an acetalde= hyde acetal group content equivalent to about 73.9 per cent by weight of polyvinyl acetaldehyde acetal. The polyvinyl acetal portion of the resin was therefore made up of about 19.7 per cent by moles of polyvinyl formaldehyde acetal and about 80.3 per cent by moles of polyvinyl acetaldehyde acetal. The resin was soluble in acetone to an extent which permitted coating a film or sheet from the resin. Example 2 50 parts (.58 mol as monomer) of polyvinyl acetate (45 centipoises), 50 parts of ethyl alcohol, 90 parts of ethyl acetate, 17 parts (.385 mol. as

'monomer) of paracetaldehyde, 2.9 parts (.098

equivalent to about 4.1% by weight of polyvinyl acetate, a formaldehyde acetal group content equivalent to about 13.9 per cent by weight of polyvinyl formaldehyde acetal, and an acetaldehyde acetal group content equivalent to about 69.9 per cent of polyvinyl acetaldehyde acetal. The polyvinyl acetal portion of the resin was therefore made up of about 18.5 per cent by moles of polyvinyl formaldehyde acetal and 81.5 per cent by moles of polyvinyl acetaldehyde acetal. The resin was soluble in acetone to an extent which permitted coating 1?. film or sheet from the resin.

Example 3 1300 parts- (15.1 mol. as monomer) of a polyvinyl acetate (45 centipoises) 1700 parts of ethyl acetate, 2250 parts of ethyl alcohol (25%) and 48 parts (1.57 mol. as monomer) of paraformaldehyde (trioxymethylene) were placed in a vessel equipped with a reflux condenser and a means of agitation, and the contents brought to a temperature of about 70 C. by means of steam heating. 182.25 parts of sulfuric acid (sp. g. 1.84)

dissolved in 51.5 parts of water were added, and the whole was heated at about 70 C. for about five hours, agitating throughout. At this point, 266.4 parts (6.05 mol. as monomer) of paracetaldehyde were added and heating at about 70 C. with agitation was continued for a furtherperiod of twenty hours. The contents of the reaction vessel were neutralized with ammonium hydroxide and diluted was water precipitating the resin as a cake. pieces and repeatedly washed with hot water until the resin was free from solvents, salts and other impurities. The resin, upon analysis, showed a hydroxyl group content equivalent to about 10.1 per cent by weight of polyvinyl alcohol, an acetategroup content equivalent to about 3.2 per cent by weight of polyvinyl acetate,

the remainder of the weight of the resin .being polyvinyl acetal. The polyvinyl acetal portion of the resin was made up about per cent by moles of polyvinyl acetaldehyde acetal and about 20 per cent by moles of polyvinyl formaldehyde acetal. The resin was not quite soluble in acetone, but could be made to dissolve by admixing small amounts-of other solvents, such as alcohols, with the acetone." I

Examples of the preparation of polyvinyl butyraldehyde acetal resins may be found in U. 8. Patent 2,044,730. Examples 2, 5 and 6; British Patent 466,598, Example 5; French Patent 813,-. 303, Example 1; French Patent 813,514, Examples 1, 2, 3 and 4; and British Patent 459,878, Examples 1, 2, 5, 6, 7, 8, 9 and 10.

An additional example of the preparation of a polyvinyl butyraldehyde acetal resin is as follows:

23.6 lbs. of polyvinyl acetate, the viscosity of whosemolar solution in benzene was 45-centipulses, was dissolved in 56.5 lbs of ethyl alcohol. To this solution was added 7.9 lbs. of bu-. v

The cake was cut into small,

at 40 C., the

EXAMPLE 2l.-Polyvinyl butyraldehyde acetal cyclohexanone ketal resin 500 g. (5.8 mol.) of polyvinyl acetate, of viscosity 45, were dissolved in 2500 cc. of methyl alcohol and to this mixture were added 1000 cc. of a 3.3 methanol and 350 gm-sfof cyclohexanone. The resulting solution-was allowed to stand 'for 18 hours, at the end of which time a ielly-like'cake had formed. vOne-half of this solid resinous mass was treated with 350 gms. of butyraldehyde and 500 cc. of methanol. After 24 hours reaction precipitated resinous mass was removed, dissolved The dry material contained 1.0% polyvinyl acetate and 6.42% polyvinyl alcohol. The resin was soluble in a mixture of 90% acetone and 10% methanol, from which itwas coated to give a sheet showing unusually low moisture absorption, high flexibility, and moderately low tensile strength.

N solution of dryfhydrogen chloride in in acetone, and precipitated.

and at least parts, approximately,

Examu: WP-Polyvinyl butm'uldehyde acetal cuclohezanonc ketal resin "2260 g. of polyvinyl acetate, of viscosity 45. were dissolved in 11,325 cc. of methanol, and 3945 cc. of a 2.88 N solution of dry HCl in methanol were added. After about minutes, 1540 gms. oi cyclohexanone were added. After an additional period of 7 hours, 1585 gms. of butyraldehyde were added to the gelatinous material and the mixture was allowed to stand at 40 C. for 24 hours. separated by decantation, dissolved in acetone, and precipitated in water. 1591 gms. of product were obtained of the following analysis:

Per cent Polyvinyl aceta 2 Polyvinyl almhnl 9.3

This resin showed the same general properties as the product of Example 21, i e., very low moisture absorption, and high flexibility, but soft and stretchy at elevated temperatures.

What I claim as secured by Letters Patent of the United States is:

1. A transparent, rubbery sheet comprising parts of a polyvinyl acetal resin in which a predominating proportion of the acetal groups are.

butyraldehyde acetal groups, and at least 40 parts, approximately, of .tributyl citrate as an elasticizer therefor.

2. A transparenhrubberysheet comprising 100 parts or a polyvinyl butyraldehyde acetal resin of tributyl as citrate as an elasticizer therefor.

HENRY B. SMII'H.

The insoluble resinous mass was my invention and desire to be 

